007 wrote:Nightfire Source will be available on Steam? maybe not.. or one of the requirements for use of Source engine? or i'm completely wrong?

You need a Source Engine game first, then you can play any source mod. Nightfire could well be listed on Steam, but I don't think it's time for that yet. There is the GreenLight system, where the community decides if the game is fit for the main Steam store. As this is supposed to stay free (I hope), it is unlikely that this will be done (for example, see the GE:Source project).